Deflectable platens and associated methods

ABSTRACT

A deflectable platen including a first layer formed of a material having a first coefficient of thermal expansion (CTE), and a second layer bonded to the first layer and having a second CTE, the second layer including a plurality of electrodes embedded therein for facilitating electrostatic clamping of wafers to the second layer, wherein the second CTE is different than the first CTE.

FIELD OF THE DISCLOSURE

Embodiments of the present disclosure relate generally to the field ofsemiconductor device fabrication, and more particularly to deflectableplatens for facilitating effective electrostatic clamping ofsemiconductor wafers.

BACKGROUND OF THE DISCLOSURE

Semiconductor wafers are typically disposed on flat platens during ionimplantation and certain other processes performed during semiconductordevice fabrication. Commonly, a semiconductor wafer is secured to aplaten via electrostatic clamping, wherein an electrical voltage isapplied between embedded electrodes in a platen and a resulting electricfield holds a semiconductor wafer to the platen. Electrostatic clampingis preferable to mechanical clamping since mechanical clamping candamage and/or contaminate a semiconductor wafer.

The ability of a platen to securely clamp a semiconductor wafer theretovia electrostatic clamping largely depends on the proximity of thebottom surface of the semiconductor wafer to the top surface of theplaten. Ideally, both of these surfaces are planar and are disposed inflat, continuous contact with one another. In some cases, asemiconductor wafer may be warped (e.g., deflected up to 20 thousandthsof an inch (thou)), resulting in a relatively large gap between a bottomsurface of the semiconductor wafer and a top surface of a platen. Thismay result in weak or ineffective electrostatic clamping. This problemcan be exacerbated if the semiconductor wafer and the platen are exposedto high temperature processes (e.g., during high temperature ionimplantation), wherein incoherent deflection of the semiconductor waferand the platen may cause the gap therebetween to increase in size.

Thus, minimizing surface-to-surface proximity between a semiconductorwafer and a platen is desirable for facilitating secure electrostaticclamping therebetween. With respect to these and other considerationsthe present improvements may be useful.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form. This Summary is not intended to identify key featuresor essential features of the claimed subject matter, nor is this Summaryintended as an aid in determining the scope of the claimed subjectmatter.

A deflectable platen in accordance with a non-limiting embodiment of thepresent disclosure may include a first layer formed of a material havinga first coefficient of thermal expansion (CTE), and a second layerbonded to the first layer and having a second CTE, the second layerincluding a plurality of electrodes embedded therein for facilitatingelectrostatic clamping of wafers to the second layer, wherein the secondCTE is different than the first CTE.

A deflectable platen in accordance with another non-limiting embodimentof the present disclosure may include a first layer formed of a materialhaving a first CTE, a second layer bonded to the first layer and havinga second CTE greater than the first CTE, the second layer including aplurality of electrodes embedded therein for facilitating electrostaticclamping of wafers to the second layer, and a heat trace disposedbetween the first layer and the second layer and adapted to controllablyheat the first layer and the second layer.

A method of deflecting a platen in accordance with a non-limitingembodiment of the present disclosure may include providing a first layerformed of a material having a first CTE, and providing a second layerbonded to the first layer and having a second CTE, the second layerincluding a plurality of electrodes embedded therein for facilitatingelectrostatic clamping of wafers to the second layer, wherein the secondCTE is different than the first CTE, and one of heating the first andsecond layers to a temperature in a range of 300 degrees Celsius to 600degrees Celsius and cooling the first and second layers to a temperaturein a range of −50 degrees Celsius to −150 degrees Celsius.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example, various embodiments of the disclosed apparatus willnow be described, with reference to the accompanying drawings, wherein:

FIG. 1A is a cross sectional side view illustrating an exemplaryembodiment of a deflectable platen in accordance with the presentdisclosure with a semiconductor wafer disposed thereon;

FIG. 1B is a cross sectional side view illustrating the deflectableplaten of FIG. 1A in a deflected state with the semiconductor waferdisposed thereon;

FIG. 1C is a cross sectional side view illustrating the deflectableplaten of FIG. 1A having been elastically returned to an undeflectedstate;

FIG. 2 is a flow diagram illustrating a method of deflecting a platen inaccordance with an embodiment of the present disclosure;

FIG. 3A is a cross sectional side view illustrating another exemplaryembodiment of a deflectable platen in accordance with the presentdisclosure with a semiconductor wafer disposed thereon;

FIG. 3B is a cross sectional side view illustrating the deflectableplaten of FIG. 3A in a deflected state with the semiconductor waferdisposed thereon;

FIG. 3C is a cross sectional side view illustrating the deflectableplaten of FIG. 3A plastically maintained in a deflected state;

FIG. 4 is a flow diagram illustrating another method of deflecting aplaten in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

The present embodiments will now be described more fully hereinafterwith reference to the accompanying drawings, wherein some embodimentsare shown. The subject matter of the present disclosure may be embodiedin many different forms and are not to be construed as limited to theembodiments set forth herein. These embodiments are provided so thisdisclosure will be thorough and complete, and will fully convey thescope of the subject matter to those skilled in the art. In thedrawings, like numbers refer to like elements throughout.

Referring to FIG. 1A, a cross-sectional side view illustrating adeflectable platen 10 (hereinafter “the platen 10”) in accordance withan exemplary embodiment of the present disclosure is shown. The platen10 may be elastically deformable (as further described below) forproviding a close clearance relationship between a top surface of theplaten 10 and a bottom surface of a warped or bowed semiconductor waferdisposed upon the platen 10 to facilitate effective electrostaticclamping therebetween.

The platen 10 may include a generally planar first layer 12 formed of afirst material and a generally planar second layer 14 formed of a secondmaterial disposed atop the first layer 12. The first material may have afirst coefficient of thermal expansion (CTE) and the second material mayhave a second CTE, wherein the second CTE may be greater than the firstCTE. The first and second layers 12, 14 may be flatly bonded together,such as by brazing or other techniques suited to bonding the first andsecond materials together. In various embodiments, the platen 10 mayinclude a heat trace 15 disposed or “sandwiched” between the first andsecond layers 12, 14. The heat trace 15 may include an electricalheating element (e.g., one or more wires, cables, plates, tapes, etc.)connected to an electrical power source (not shown). The heat trace 15may be flexible and may be adapted to withstand deflection of the platen10 up to at least 20 thou (as described below), for example. Byactivating the heat trace 15, the abutting first and second layers 12,14 of the platen 10 may be controllably heated as further describedbelow.

In one example, the first layer 12 of the platen 10 may be formed of amaterial having a CTE less than 6.0×10⁻⁷/° C. (e.g., between 2.0×10⁻⁷/°C. and 4.0×10⁻⁷/° C.). In a specific example, first layer 12 may beformed of quartz. The present disclosure is not limited in this regard.The first layer 12 may alternatively be formed of other relativelylow-CTE materials, including, and not limited to, carbon, silicon,silicon nitride, silicon carbide, aluminum nitride, INVAR, KOVAR,molybdenum, tungsten, tantalum, titanium, and their alloys. In oneexample, the second layer 14 of the platen 10 may be formed of amaterial having a relatively higher CTE than the first layer 12 (e.g., amaterial having a CTE in a range between 6.0×10⁻⁷/° C. and 8.0×10⁻⁷/°C.). In a specific example, second layer 14 may be formed of a ceramic,including, and not limited to, aluminum oxide. The present disclosure isnot limited in this regard. The second layer 14 may alternatively beformed of other relatively higher-CTE materials including, and notlimited to, aluminum, silver, copper, and their alloys.

The second layer 14 of the platen 10 may have a plurality of electrodes16 embedded therein. The electrodes 16 may be connected to a source ofelectrical power (not shown) and may be arranged and configured tooperate in the manner of a conventional electrostatic clamp familiar tothose of skill in the art. Particularly, by applying an electricalvoltage across the electrodes 16, an electrical field can be generatedand may hold a semiconductor wafer 18 (hereinafter “the wafer 18”) tothe platen 10 via electrostatic force. The strength of the electrostaticforce acting on the wafer 18 will depend partly on the proximity of thewafer 18 to the electrodes 16. Ideally, the contour of the bottomsurface of the wafer 18 will match or nearly match the contour of thetop surface of the platen 10 (e.g., if both surfaces are planar ornearly planar), thus establishing a shortest possible distance betweenthe electrodes 16 and the wafer 18 to provide strong electrostaticcoupling therebetween. In some cases, a wafer, such as the wafer 18shown in FIG. 1A, may be warped or bowed (e.g., deflected up to, andpossibly greater than, 20 thou) and may present a concave bottom surfaceto the generally planar top surface of the platen 10 (the deflection ofthe wafer 18 as shown in FIG. 1A is exaggerated for purposes ofillustration). The resulting gap 20 between the wafer 18 and the platen10 may attenuate the electrostatic force acting on the wafer 18, thusresulting in poor electrostatic clamping between the platen 10 and thewafer 18.

Referring to FIG. 1B, the platen 10 is shown in a deflected state.Particularly, the heat trace 15 has been activated, thus heating thefirst and second layers 12, 14 of the platen 10. Since the CTE of thesecond layer 14 is greater than the CTE of the first layer 12, theheated second layer 14 may expand more (i.e., more quickly and/or to agreater degree) than the heated first layer 12, resulting in a convexdeflection of the platen 10. Thus, the contour of the top surface of theplaten 10 may be made to more closely match the contour of the bottomsurface of the wafer 18 to reduce the size of the gap 20 therebetweenrelative to the undeflected state of the platen 10 shown in FIG. 1A. Invarious examples, the platen 10 may be heated to a temperature between300 degrees Celsius and 600 degrees Celsius. In a particularnon-limiting example, the platen 10 may exhibit a deflection of 18 thouwhen heated to a temperature of 500 degrees Celsius. The presentdisclosure is not limited in this regard. The smaller gap 20 and closerproximity of the electrodes 16 to the wafer 18 facilitated by thedeflected platen 10 provide a stronger electrostatic force acting on thewafer 18 relative to the electrostatic force applied by the undeflectedplaten 10 shown in FIG. 1A, thus resulting in better electrostaticcoupling between the platen 10 and the wafer 18.

The degree of deflection in the heated platen 10 will depend on a numberof factors, including, and not limited to, the CTEs of the first andsecond layers 12, 14, the amount of heat applied to the first and secondlayers 12, 14, the diameters of the first and second layers 12, 14, andthe thicknesses of the first and second layers 12, 14. In a non-limitingembodiment, the thickness of the first layer 12 may be 4 millimeters andthe thickness of the second layer 14 may be 4 millimeters. In anothernon-limiting embodiment, the thickness of the first layer 12 may be 6millimeters and the thickness of the second layer 14 may be 4millimeters. In another non-limiting embodiment, the thickness of thefirst layer 12 may be 8 millimeters and the thickness of the secondlayer 14 may be 4 millimeters. The present disclosure is not limited inthis regard, and the thicknesses of the first and second layers 12, 14may be varied from those mentioned above. Additionally, while the platen10 has been described as including the integrated heat trace 15 forcontrollably heating the platen 10, embodiments of the platen 10 arecontemplated wherein the heat trace 15 is omitted and the platen 10 isheated by an external heat source (e.g., an oven).

In various embodiments, the deflection stress on the platen 10 duringheating may be less than the yield strength of the materials of thefirst and/or second layers 12, 14. Thus, when the heat trace 15 (orother heat source) is deactivated and the platen 10 is allowed to coolto room temperature, the platen 10 may return to its original, generallyplanar state as shown in FIG. 1C. Thus, by varying the amount of heatapplied to the first and second layers 12, 14, the platen 10 may becontrollably deflected to varying degrees (e.g., from 0 to 20 thou) tomatch or approach the contour of wafers having various degrees ofdeflection disposed thereon to provide effective electrostatic clampingtherebetween.

Referring to FIG. 2, a flow diagram illustrating an exemplary method fordeflecting a platen in accordance with the present disclosure is shown.The method will now be described in conjunction with the illustrationsof the platen 10 shown in FIGS. 1A-1C.

At block 100 of the exemplary method, the first layer 12 may be providedand may be formed of a material having a first CTE. At block 110 of themethod, the second layer 14 may be provided and may be formed of amaterial having a second CTE, and the second layer 14 may be flatlybonded to the first layer 12, such as by brazing or other appropriatetechniques as described above. The second CTE may be greater than thefirst CTE. In various examples, the first layer 12 may be formed of amaterial having a CTE less than 6.0×10⁻⁷/° C. (e.g., between 2.0×10⁻⁷/°C. and 4.0×10⁻⁷/° C.) and the second layer 14 may have a CTE in a rangebetween 6.0×10⁻⁷/° C. and 8.0×10⁻⁷/° C. The second layer 14 may have theplurality of electrodes 16 embedded therein. The electrodes 16 may beconnected to a source of electrical power and may be arranged andconfigured to operate in the manner of a conventional electrostaticclamp familiar to those of skill in the art.

At block 120 of the exemplary method, the heat trace 15 may be disposed(e.g., sandwiched) between the first layer 12 and the second layer 14.This may be performed before or during bonding of the second layer 14 tothe first layer 12. The heat trace 15 may include an electrical heatingelement (e.g., one or more wires, cables, plates, tapes, etc.) connectedto an electrical power source.

At block 130 of the exemplary method, the heat trace 15 may beactivated, thus heating the first and second layers 12, 14. Since theCTE of the second layer 14 is greater than the CTE of the first layer12, the heated second layer 14 may expand more (i.e., more quicklyand/or to a greater degree) than the heated first layer 12, resulting ina convex deflection of the platen 10. Thus, as shown in FIG. 1B, thecontour of the top surface of the platen 10 may be made to more closelymatch the contour of the bottom surface of the wafer 18 to reduce thesize of the gap 20 therebetween relative to the undeflected state of theplaten 10 shown in FIG. 1A.

Referring to FIG. 3A, a cross-sectional side view illustrating adeflectable platen 200 (hereinafter “the platen 200”) in accordance withanother exemplary embodiment of the present disclosure is shown. Theplaten 200 may be plastically deformable (as further described below)for providing a close clearance relationship between a top surface ofthe platen 200 and a bottom surface of a warped or bowed semiconductorwafer disposed upon the platen 200 to facilitate effective electrostaticclamping therebetween.

The platen 200 may include a generally planar first layer 212 formed ofa first material and a generally planar second layer 214 formed of asecond material disposed atop the first layer 212. The first materialmay have a first coefficient of thermal expansion (CTE) and the secondmaterial may have a second CTE, wherein the first CTE may be greaterthan the second CTE. The first and second layers 212, 214 may be flatlybonded together, such as by epoxy or other techniques suited to bondingthe first and second materials together.

In one example, the first layer 212 of the platen 200 may be formed of amaterial having a CTE greater than 20.0×10⁻⁷/° C. (e.g., a materialhaving a CTE of approximately 24.0×10⁻⁷/° C.). In a specific example,first layer 212 may be formed of porous aluminum alloy. The presentdisclosure is not limited in this regard. The first layer 212 mayalternatively be formed of other relatively high-CTE materials,including, and not limited to, aluminum, silver, copper, and theiralloys. In one example, the second layer 214 of the platen 200 may beformed of a material having a relatively lower CTE than the first layer112 (e.g., a material having a CTE in a range between 6.0×10⁻⁷/° C. and8.0×10⁻⁷/° C.). In a specific example, second layer 214 may be formed ofa ceramic, including, and not limited to, aluminum oxide. The presentdisclosure is not limited in this regard. The second layer 214 mayalternatively be formed of other relatively lower-CTE materialsincluding, and not limited to, carbon, silicon, silicon nitride, siliconcarbide, aluminum nitride, INVAR, KOVAR, molybdenum, tungsten, tantalum,titanium, and their alloys.

The second layer 214 of the platen 200 may have a plurality ofelectrodes 216 embedded therein. The electrodes 216 may be connected toa source of electrical power (not shown) and may be arranged andconfigured to operate in the manner of a conventional electrostaticclamp familiar to those of skill in the art. Particularly, by applyingan electrical voltage across the electrodes 216, an electrical field canbe generated and may hold a semiconductor wafer 218 (hereinafter “thewafer 218”) to the platen 200 via electrostatic force. The strength ofthe electrostatic force acting on the wafer 218 will depend partly onthe proximity of the wafer 218 to the electrodes 216. Ideally, thecontour of the bottom surface of the wafer 218 will match or nearlymatch the contour of the top surface of the platen 200 (e.g., if bothsurfaces are planar), thus establishing a shortest possible distancebetween the electrodes 216 and the wafer 218 to provide strongelectrostatic coupling therebetween. In some cases, a wafer, such as thewafer 218 shown in FIG. 3A, may be warped or bowed (e.g., deflected upto, and possibly greater than, 20 thou) and may present a concave bottomsurface to the generally planar top surface of the platen 200 (thedeflection of the wafer 218 as shown in FIG. 3A is exaggerated forpurposes of illustration). The resulting gap 220 between the wafer 218and the platen 200 may attenuate the electrostatic force acting on thewafer 218, thus resulting in poor electrostatic clamping between theplaten 200 and the wafer 218.

Referring to FIG. 3B, the platen 200 is shown in a deflected state.Particularly, the platen has been rapidly and drastically cooled. In anon-limiting example, the platen 200 may be immersed in liquid nitrogen.The present disclosure is not limited in this regard. Since the CTE ofthe first layer 212 is greater than the CTE of the second layer 214, thecooled first layer 212 may contract more (i.e., more quickly and/or to agreater degree) than the cooled second layer 214, resulting in a convexdeflection of the platen 200. Thus, the contour of the top surface ofthe platen 200 may be made to more closely match the contour of thebottom surface of the wafer 218 to reduce the size of the gap 220therebetween relative to the undeflected state of the platen 200 shownin FIG. 3A. In various examples, the platen 200 may be cooled to atemperature between −50 degrees Celsius and −150 degrees Celsius. In aparticular non-limiting example, the platen 200 may exhibit a deflectionof 22 thou when cooled to a temperature of −100 degrees Celsius. Thepresent disclosure is not limited in this regard. The smaller gap 220and closer proximity of the electrodes 216 to the wafer 218 facilitatedby the deflected platen 200 provide a stronger electrostatic forceacting on the wafer 218 relative to the electrostatic force applied bythe undeflected platen 200 shown in FIG. 3A, thus resulting in betterelectrostatic coupling between the platen 200 and the wafer 218.

The degree of deflection in the heated platen 200 will depend on anumber of factors, including, and not limited to, the CTEs of the firstand second layers 212, 214, the amount of cooling applied to the firstand second layers 212, 214, the diameters of the first and second layers212, 214, and the thicknesses of the first and second layers 212, 214.In a non-limiting embodiment, the thickness of the first layer 212 maybe 4 millimeters and the thickness of the second layer 214 may be 4millimeters. In another non-limiting embodiment, the thickness of thefirst layer 212 may be 6 millimeters and the thickness of the secondlayer 214 may be 4 millimeters. In another non-limiting embodiment, thethickness of the first layer 212 may be 8 millimeters and the thicknessof the second layer 214 may be 4 millimeters. The present disclosure isnot limited in this regard, and the thicknesses of the first and secondlayers 212, 214 may be varied from those mentioned above.

In various embodiments, the deflection stress on the platen 200 duringcooling may be greater than the yield strength of the material of thefirst layer 212 and/or the yield strength of the material of the secondlayer 214. Thus, when the platen 200 is allowed to warm to roomtemperature, the platen 200 may remain in its convex, deflected state asshown in FIG. 3C (i.e., plastic deformation). If, during cooling, theplaten 200 was deflected beyond a desired, target amount of deflection(i.e., made more convex than desired), the platen 200 may be heated,such as by an external heat source (e.g., an oven). Since the CTE of thefirst layer 212 is greater than the CTE of the second layer 214, theheated first layer 212 may expand more (i.e., more quickly and/or to agreater degree) than the heated second layer 214, resulting in a reversedeflection of the platen 200 (i.e., relative to when the platen 200 wascooled), thus reducing the convexity of the platen 200. The deflectionstress on the platen 200 during heating may be greater than the yieldstrength of the material of the first layer 212 and/or greater than theyield strength of the material of the second layer 214, thus resultingin plastic deformation. The above-described cooling and heating of theplaten 200 may be repeated as necessary until a desired amount ofdeflection in the platen 200 is achieved. Thus, by varying the amount ofcooling and heating applied to the first and second layers 212, 214, theplaten 200 may be controllably deflected to varying degrees (e.g., from0 to 22 thou) to match or approach the contour of wafers having variousdegrees of deflection disposed thereon to provide effectiveelectrostatic clamping therebetween.

Referring to FIG. 4, a flow diagram illustrating an exemplary method fordeflecting a platen in accordance with the present disclosure is shown.The method will now be described in conjunction with the illustrationsof the platen 200 shown in FIGS. 3A-3C.

At block 300 of the exemplary method, the first layer 212 may beprovided and may be formed of a material having a first CTE. At block310 of the method, the second layer 214 may be provided and may beformed of a material having a second CTE, and the second layer 214 maybe flatly bonded to the first layer 212, such as by epoxy or otherappropriate techniques as described above. The first CTE may be greaterthan the second CTE. In various examples, the first layer 212 may beformed of a material having a CTE in a range between 6.0×10⁻⁷/° C. and8.0×10⁻⁷/° C. and the second layer 214 may have a CTE less than6.0×10⁻⁷/° C. (e.g., between 2.0×10⁻⁷/° C. and 4.0×10⁻⁷/° C.). Thesecond layer 214 may have the plurality of electrodes 216 embeddedtherein. The electrodes 216 may be connected to a source of electricalpower and may be arranged and configured to operate in the manner of aconventional electrostatic clamp familiar to those of skill in the art.

At block 320 of the exemplary method, the platen 200 may be rapidly anddrastically cooled. In a non-limiting example, the platen 200 may beimmersed in liquid nitrogen. The present disclosure is not limited inthis regard. Since the CTE of the first layer 212 is greater than theCTE of the second layer 214, the cooled first layer 212 may contractmore (i.e., more quickly and/or to a greater degree) than the cooledsecond layer 214, resulting in a convex deflection of the platen 200.Thus, the contour of the top surface of the platen 200 may be made tomore closely match the contour of the bottom surface of the wafer 218 toreduce the size of the gap 220 therebetween relative to the undeflectedstate of the platen 200 shown in FIG. 3A.

As will be appreciated by those of ordinary skill in the art, theabove-described deflectable platens 10, 200 and related methods providedistinct advantages relative to conventional platens. For example, inthe case of the elastically deformable platen 10 described above, theplaten 10 can be dynamically deflected through the selective applicationof heat (e.g. via heat trace 15) to rapidly and conveniently facilitateeffective electrostatic clamping with wafers having various degrees ofdeflection. In the case of the plastically deformable platen 200described above, the platen 200 can be deformed once (via theapplication of cooling and heating) to achieve a desired degree ofdeflection and will thereafter retain its deflected shape to facilitateeffective electrostatic clamping with similarly deflected wafers in theabsence of any further cooling or heating.

The present disclosure is, not to be limited in scope by the specificembodiments described herein. Indeed, other various embodiments of andmodifications to the present disclosure, in addition to those describedherein, will be apparent to those of ordinary skill in the art from theforegoing description and accompanying drawings. Thus, such otherembodiments and modifications are intended to fall within the scope ofthe present disclosure. Furthermore, while the present disclosure hasbeen described herein in the context of a particular implementation in aparticular environment for a particular purpose, those of ordinary skillin the art will recognize its usefulness is not limited thereto.Embodiments of the present disclosure may be beneficially implemented inany number of environments for any number of purposes. Accordingly, theclaims set forth below shall be construed in view of the full breadthand spirit of the present disclosure as described herein.

1. A deflectable platen comprising: a first layer formed of a materialhaving a first coefficient of thermal expansion (CTE); and a secondlayer bonded to the first layer and having a second CTE, the secondlayer including a plurality of electrodes embedded therein forfacilitating electrostatic clamping of wafers to the second layer,wherein the second CTE is different than the first CTE.
 2. Thedeflectable platen of claim 1, wherein the second CTE is greater thanthe first CTE.
 3. The deflectable platen of claim 2, wherein the firstCTE is between 2.0×10⁻⁷/° C. and 4.0×10⁻⁷/° C., and the second CTE isbetween 6.0×10⁻⁷/° C. and 8.0×10⁻⁷/° C.
 4. The deflectable platen ofclaim 2, wherein the first layer is formed of at least one of quartz,carbon, silicon, silicon nitride, silicon carbide, aluminum nitride,INVAR, KOVAR, molybdenum, tungsten, tantalum, and titanium.
 5. Thedeflectable platen of claim 2, wherein the second layer is formed of atleast one of ceramic, aluminum, silver, and copper.
 6. The deflectableplaten of claim 1, wherein the first CTE is greater than the second CTE.7. The deflectable platen of claim 6, wherein the second CTE is between2.0×10⁻⁷/° C. and 4.0×10⁻⁷/° C., and the first CTE is between 6.0×10⁻⁷/°C. and 8.0×10⁻⁷/° C.
 8. The deflectable platen of claim 6, wherein thesecond layer is formed of at least one of quartz, carbon, silicon,silicon nitride, silicon carbide, aluminum nitride, INVAR, KOVAR,molybdenum, tungsten, tantalum, and titanium.
 9. The deflectable platenof claim 6, wherein the first layer is formed of at least one ofceramic, aluminum, silver, and copper.
 10. The deflectable platen ofclaim 1, further comprising a heat trace disposed between the firstlayer and the second layer and adapted to controllably heat the firstlayer and the second layer.
 11. The deflectable platen of claim 10,wherein the heat trace comprises at least one of a wire, a cable, aplate, and a tape connected to a source of electrical power.
 12. Adeflectable platen comprising: a first layer formed of a material havinga first coefficient of thermal expansion (CTE); a second layer bonded tothe first layer and having a second CTE greater than the first CTE, thesecond layer including a plurality of electrodes embedded therein forfacilitating electrostatic clamping of wafers to the second layer; and aheat trace disposed between the first layer and the second layer andadapted to controllably heat the first layer and the second layer.
 13. Amethod of deflecting a platen comprising: providing a first layer formedof a material having a first coefficient of thermal expansion (CTE); andproviding a second layer bonded to the first layer and having a secondCTE, the second layer including a plurality of electrodes embeddedtherein for facilitating electrostatic clamping of wafers to the secondlayer, wherein the second CTE is different than the first CTE; and oneof: heating the first and second layers to a temperature in a range of200 degrees Celsius to 600 degrees Celsius; and cooling the first andsecond layers to a temperature in a range of −50 degrees Celsius to −150degrees Celsius.
 14. The method of claim 13, wherein the second CTE isgreater than the first CTE.
 15. The method of claim 14, wherein thefirst CTE is between 2.0×10⁻⁷/° C. and 4.0×10⁻⁷/° C., and the second CTEis between 6.0×10⁻⁷/° C. and 8.0×10⁻⁷/° C.
 16. The method of claim 14,further comprising disposing a heat trace between the first layer andthe second layer.
 17. The method of claim 13, further comprisingactivating a heat trace disposed between the first layer and the secondlayer to heat the first layer and the second layer.
 18. The method ofclaim 13, wherein the first CTE is greater than the second CTE.
 19. Themethod of claim 18, wherein the second CTE is between 2.0×10⁻⁷/° C. and4.0×10⁻⁷/° C., and the first CTE is between 6.0×10⁻⁷/° C. and 8.0×10⁻⁷/°C.
 20. The method of claim 18, wherein cooling the first and secondlayers comprises at least partially submerging the first and secondlayers in liquid nitrogen.